Space Balls

July 27, 2010

Fullerenes are large molecules composed solely of carbon. These molecules, constrained by the energetically-stable bonding angles of the carbon atom, can be shaped as spheres, ellipsoids and tubes. The spherical fullerenes (more precisely, the C60 allotrope) are often called buckyballs, an homage to Buckminster Fuller, who popularized the geodesic dome which they resemble. The fullerenes were discovered at Rice University in 1985 by Robert Curl, Harold Kroto and Richard Smalley. A patent[1] was granted to Smalley in 1993 for an electric arc process for making fullerenes.

Although the C60 fullerene was seemingly a "new composition of matter" when it was discovered, what was patented was not C60 itself, but a process to make C60. This was a good choice. Although C60 had not been found in nature at the time, I'm sure that Smalley and his collaborators realized that the conditions that existed in their reactor had likely been duplicated in nature, somewhere. According to US patent law[2],

"... a new mineral discovered in the earth or a new plant found in the wild is not patentable subject matter.

As it turns out, buckyballs are produced by something as common as a burning candle, and they are found also in carboniferous mineral deposits.[3] Now, buckyballs have been detected in space, near the remnants of a dying star.[4-6]

This discovery was facilitated by the fact that there's a star in the middle of the nebula that's illuminating it, and the nebula is at the right temperature for infrared measurements, about room temperature. This central star is a white dwarf, which is an end stage in the normal evolution of stars. At this stage, stars are expected to contain considerable quantities of carbon. The timing of the discovery may have been fortuitous, Cami thinks that the fullerenes would not have been detected if the observations had been done a few hundred years sooner, or later. He speculates that all planetary nebulae may go through a fullerene phase. The spectra are quite clear, as shown in the figure.

As are many scientific discoveries, this discovery was accidental. Co-author Jeronimo Bernard-Salas of Cornell University obtained the spectra and noted that the data were unusual. The typical carbon chains and aromatic compounds were absent. His collaborators found a match to C60 and C70 and discovered what are the largest molecules known to exist in space. Fullerenes might be important to the evolution of life in the universe.